inter roads are operated in many cold weather regions to provide transportation for communities that are otherwise only accessible by air, or to reduce travel time during the winter by providing a shorter, more direct route to the community. Winter roads frequently cross frozen bodies of water, such as lakes or rivers, and require considerable safety precautions prior to use. Manitoba Infrastructure is a unified department proactively leading the delivery of sustainable public infrastructure and services for the province of Manitoba. The department is responsible for maintaining winter roads in Manitoba and will only open a winter road once they have deemed it safe for use.

In northern Manitoba, a winter road is operated between Split Lake and Ilford. Prior to opening the road, extensive ice thickness assessment is required. To measure the ice thickness, Manitoba Infrastructure uses IceMap™, a GPR system that provides continuous measurements of ice thickness as it is towed along the ice surface. The system is deployed every few days as the ice is flooded and the thickness built up.

During the ice road construction phase a few winters ago, the operators noticed consistent anomalies in the IceMap™ data. These areas were drilled to investigate, and revealed air pockets that formed in the ice (Figure 1).

Figure 1:

IceMap™ data indicating anomalies; these were later determined to be air pockets that formed in the ice.

The mechanism creating the air pockets was believed to be the strong currents present when the ice was forming.

Air pockets can weaken the overall load-bearing capacity of the ice and could be dangerous, analogous to a sinkhole forming in the soil subsurface.

As a result of discovering the section of ice road with air pockets, Manitoba Infrastructure used the IceMap™ GPR to map out a new route which didn’t have air pockets (Figure 2). Since finding this new road, it has been the route used ever since. The GPS positioning in IceMap™ provides the means to relocate roads repeatedly.

Figure 2:

IceMap™ GPR data collected on the new route, showing no air pockets.

Data collected with IceMap™ can be used in the following ways:

For real-time analysis to direct flooding efforts

To generate a detailed ice thickness report, showing the location and extent of thin spots

Plotted in Google Earth to show the path traveled, colour–coded to show the thickness of ice

The Google Earth™ image (Figure 3) shows the old route and the new one. Thick ice is shown in blue, whereas thinner ice is shown in yellow and green. The old route shows the problem area with air pockets, as the road curves.

By using IceMap™, Manitoba Infrastructure obtains the information they need to safely open their winter roads. Safety is always the driving force and using IceMap™ helps to mitigate any risks and prevent injuries.

Figure 3:

Google Earth™ view showing the old winter road where the air pockets were found and the new route where the ice was safe to operate on.

In this case, IceMap™ GPR was able to identify the problem area and, rather than allocating resources to fix the problem, IceMap™ operators were able to quickly find a safer, alternate route for the winter road.